PHOTOSHOP - resampling can create halo that shouldn't be there

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  • Updated 3 years ago
  • (Edited)
Take this image:


Resize it:


Here's a detail, zoomed in:


Notice the red halo? It's caused by a red background that has 1 % opacity. The same original image resized in GIMP produces no halo (and this is the correct result):


Detail, zoomed in:


The red halo that PS produces is incorrect, so this proves there's a bug in PS. The mistake is that it gives all old pixels' RGB the same weight regardless of opacity when doing a resize with interpolation. Adobe has apparently noticed that it needs to weight with opacity in the special case of opacity = 0. In other words, PS correctly ignores fully transparent pixels. Analoguously it should almost ignore almost transparent pixels, but it doesn't. GIMP and Paint.Net does, and they are right.
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Kjell Rilbe

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Posted 3 years ago

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Photo of Kjell Rilbe

Kjell Rilbe

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Someone keeps removing the word "bug" in the subject title. Why? This is an obvious bug, no question about it.